Michels KB, Rothman KJ. Update on unethical use of placebos in randomised trials. Bioethics. 2003 Apr;17(2):188-204.
Allan JS, Kanda P, Kennedy RC, Cobb EK, Anthony MS, Eichberg JW. Isolation and characterization of simian immunodeficiency virus from two subspecies of African green monkeys. Aids Res Hum Retrovir. 1990 Mar;6(3):275-85.
Cann CI, Fried MP, Rothman KJ. Epidemiology of squamous-cell cancer of the head and neck. Otolaryngol Clin N Am. 1985 Aug 1;18(3):367-88.